A plane polishing apparatus for polishing a surface of a disk-shaped workpiece such as a semiconductor wafer has, for example, a lap 2 rotatably installed to a base portion 1a of a machine body 1, and carriers 3 that are ascended and descended by air cylinders 5 and are installed to a movable portion 1b that can be shuttled between the lap 2 and a carrying in/out portion 4 as shown in FIG. 3 and FIG. 4. Workpieces W are retained to the bottom surfaces of the carriers 3 by such a method as adhesion or suction, and the workpieces W are pressed against a working surface of the turning lap 2 to polish them.
In the polishing apparatus mentioned above, generally, the lap 2 gradually wears and loses its flatness as it polishes workpieces, with resultant deterioration in polishing accuracy. Hence, the flatness is restored by periodically dressing the working surface of the lap 2 by a dresser 6.
As can be seen from FIG. 5, the dresser 6 has a dressing member 9 such as, for example, an annular grindstone, that is attached to the bottom surface of a round dressing head 8 provided at the distal end of a support arm 7. With the dressing member 9 pressed against the working surface of the lap 2, the lap 2 and the dressing head 8 are turned while supplying a polishing solution such as an abrasive slurry, thereby dressing the lap.
Diverse foreign matters are generated during the dressing process of the lap 2, and the foreign matters are apt to adhere to the dresser 6. Foreign matters includes, for instance, coagulated abrasive grains in the slurry, abrasive grains peeled off from the dressing member 9, and chips of ground polishing pads. These attachments come off during the dressing process of the lap 2, adversely affecting the dressing work or causing other problems such as deteriorated dressing accuracy. Hence, it is desirable to remove the foreign matters from the dresser.